Method of dispersing anatase titanium dioxide for penetration in concrete structures to reduce pollutants

ABSTRACT

Methods for embedding photocatalytic titanium dioxide in concrete surfaces to reduce pollutants via photocatalytic reactions are provided herein. One method includes mixing a solvent compound with an anatase titanium dioxide (TiO 2 ) photocatalyst, applying an amount of concrete treatment compound to an upper surface of the concrete, the concrete treatment compound comprising a mixture of a liquid carrier compound with the anatase titanium dioxide (TiO 2 ) photocatalyst.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 16/564,579 filed on Sep. 9, 2019, which is a divisional of U.S.patent application Ser. No. 15/290,305 filed on Oct. 11, 2016 (now U.S.Pat. No. 10,407,351 issued on Sep. 10, 2019), which is acontinuation-in-part of U.S. patent application Ser. No. 14/207,341filed on Mar. 12, 2014 (now U.S. Pat. No. 9,493,378 issued on Nov. 15,2016), which in turn claims the priority benefit of U.S. provisionalapplication No. 61/780,626 filed on Mar. 13, 2013, the disclosures ofwhich are incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present invention relates primarily to concrete road construction,although it can apply to any horizontal or vertical concrete structures.It is a method of impregnating the concrete with a photocatalytictitanium dioxide catalyst that reacts with nitrogen oxides and otherpollutants to chemically alter them into non-hazardous or less hazardousmaterials through photocatalytic oxidation (PCO) and/or reductionreaction. One or more solvent compounds are used to disperse the anataseform of titanium dioxide so that the photocatalytic titanium dioxidecatalyst can penetrate the concrete. The solvent(s) utilized may beorganic or inorganic.

SUMMARY

In some embodiments, the present technology is directed to a method thatincludes applying an amount of concrete treatment compound to an uppersurface of the concrete, the concrete treatment compound comprising amixture of a liquid carrier compound with a titanium dioxide (TiO₂)photocatalyst. One or more organic or inorganic solvent compounds areused to disperse the anatase form of TiO₂ so that the concrete treatmentcompound can penetrate the concrete.

In some embodiments, the present technology is directed to a method thatincludes applying a photocatalytic compound to concrete, wherein thephotocatalytic compound is capable of uniformly penetrating the concretedown to a depth of at least an eighth of an inch relative to an uppersurface of the concrete. The penetration is due, at least in part, tothe solvent compounds used to disperse the anatase form of TiO₂ in thephotocatalytic compound. In other embodiments, the penetration may beless than an eighth of an inch.

In some embodiments, the present technology is directed to a concretetreatment compound comprising an amount of a carrier liquid mixed withan amount of a photocatalyst, wherein the carrier liquid is capable ofpenetrating concrete down to a depth of at least an eighth of an inchrelative to an upper surface of the concrete. In other embodiments, thepenetration may be less than an eighth of an inch.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, where like reference numerals refer toidentical or functionally similar elements throughout the separateviews, together with the detailed description below, are incorporated inand form part of the specification, and serve to further illustrateembodiments of concepts that are included in the claimed disclosure, andexplain various principles and advantages of those embodiments.

The methods and systems disclosed herein have been represented whereappropriate by conventional symbols in the drawings, showing only thosespecific details that are pertinent to understanding the embodiments ofthe present disclosure so as not to obscure the disclosure with detailsthat will be readily apparent to those of ordinary skill in the arthaving the benefit of the description herein.

FIG. 1 is a flowchart of an exemplary method of treating concrete toreduce the production of nitrogen oxides (NOx), volatile organiccompounds (VOC), and other pollutants by the concrete;

FIG. 2 is a method for preparing the concrete treatment compound that isto be applied to the concrete; and

FIG. 3 is a cross sectional view of a treated section of concrete.

DETAILED DESCRIPTION

While this technology is susceptible of embodiment in many differentforms, there is shown in the drawings and will herein be described indetail several specific embodiments with the understanding that thepresent disclosure is to be considered as an exemplification of theprinciples of the technology and is not intended to limit the technologyto the embodiments illustrated.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an,” and the are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

It will be understood that like or analogous elements and/or components,referred to herein, may be identified throughout the drawings with likereference characters. It will be further understood that several of thefigures are merely schematic representations of the present technology.As such, some of the components may have been distorted from theiractual scale for pictorial clarity.

The present technology is embodied in some instances as a method ofembedding photocatalytic TiO₂ nanoparticles into horizontal and verticalconcrete structures that are either already in place or in the processof curing. It is envisioned that the process may be used for allconcrete structures, but particularly those in close proximity to roadsand highways. The introduction of TiO₂ is by impregnation into concretestructures using specialized multi-purpose concrete curing andpreservation products, hereinafter referred to as a “concrete treatmentcompound.”

An advantage of the present technology is that it provides a method ofdispersing anatase TiO₂ with one or more organic or inorganic solventcompounds so that the concrete treatment compound can penetrate intoconcrete, without the need for the concrete treatment compound to complywith either federal or national regulations regarding volatile organiccompounds (VOCs). The concrete treatment compound can be created on theconstruction site or the job site where the concrete pavement beingtreated is located. This can be done by mixing the anatase TiO₂ with oneor more solvent compounds on site.

Another advantage of the present technology is that it provides a methodof introducing photocatalytic oxidation technology into existingconcrete structures, without the prohibitive cost and disruption ofremoving said structures and replacing them with new concrete.

Another advantage of the present technology is that it provides a methodof economically introducing photocatalytic oxidation technology intojust the upper layers of freshly placed concrete, eliminating theprohibitive cost of mixing expensive titanium dioxide into the entireconcrete mix.

Another advantage of the present technology is that the concretetreatment compounds uniformly impregnates the concrete at depths greatenough that normal wear of the upper surfaces will expose underlyingphotocatalytic reactive layers to the surface, so that thepollution-reducing capability is self-regenerated (e.g., remainsconsistent or viable) throughout the lifespan of the concrete structure.

Another advantage of the present technology is that the concretetreatment compounds simultaneously seals and hardens the concrete andfills voids in its structure to increase resistance to water damage,chloride ion penetration, de-icing salts, and freeze/thaw damage.Sealing of the concrete may also improve long-term photocatalyticperformance. Indeed, residual salt and water build-up on traditionalconcrete structures can interfere with photocatalytic oxidation. Theseprotective effects are provided by a liquid carrier compound, into whichthe TiO₂ is mixed.

The present technology contemplates a method of embedding photocatalyticTiO₂ nanoparticles, via delivery using concrete treatment compounds,into horizontal and/or vertical concrete structures that are eitheralready in place or in the process of curing. It is envisioned that theprocess may be used for all concrete structures, but particularly roadsand highways and structures in nearby proximity to them.

The introduction of TiO₂ is by impregnation into concrete structuresusing specialized concrete treatment compounds, resulting in thecreation of a photocatalytic reactive layer at the surface of thestructure and a uniform distribution of TiO₂ nanoparticles in the upperlayers of the concrete to depths as great as one half (0.5) inches. Insome embodiments, the impregnation or embedding of the nanoparticles isuniform and extends to a depth of from approximately one eighth of aninch to approximately one quarter of an inch relative to an uppersurface of the concrete. The impregnation or embedding is due, at leastin part, to the dispersion of the anatase form of TiO2 by one or moreorganic or inorganic solvent compounds.

For context, TiO₂ is an inorganic pigment and semiconductor material.TiO2 is available in an anatase form, in which the TiO₂ is composed ofsmall, isolated, and sharply developed crystals. Anatase TiO₂ needs tobe dispersed in order for it to penetrate concrete, and can be dispersedwith both a water base and solvent base carrier. Manufacturing andshipping solvent base products, for the most part, do not comply withcurrent federal and state regulations with regard to VOCs. As such,anatase TiO2 can be mixed with organic solvents on the construction siteor job site where the concrete pavement to be treated is located.Examples of organic solvent compounds include tetrachloroethylene,toluene, turpentine, acetone, methyl acetate, ethyl acetate, hexane,citrus terpenes, ethanol, methyl ethyl ketone, mineral spirits, andethyl alcohol. Other organic solvent compounds may also be used.

When exposed to ultraviolet (UV) radiation, as from sunlight, TiO₂expels an electron from the valence band to the conduction band, leavingbehind a positively charged hole. In the presence of water, as inatmospheric humidity, these positively charged holes create hydroxylradicals as shown:

OH⁻ +h+→*OH.

The hydroxyl radicals in turn oxidize nitrogen oxides as follows:

NO+*OH→NO₂+H⁺

NO₂+*OH→NO₃ ⁻+H⁺.

Other reduction effects occur with volatile organic compounds (VOC) andsome other pollutants. Since TiO₂ functions as a catalyst and is notconsumed in the reaction, the photocatalytic effect continues. If theTiO₂ is in place at the surface of concrete, it removes a significantquantity of NOx and VOCs from the environment nearest their source. IfTiO₂ is uniformly impregnated into the concrete to a given depth thepollution-reducing capability of the concrete will automatically andcontinuously self-regenerate as the surface layers are subjected to thenormal wear of traffic and other environmental factors.

Other reduction effect occurs with volatile organic compounds (VOC) andsome other pollutants. Since the TiO₂ functions as a catalyst and is notconsumed in the reaction, the photocatalytic effect can continue. If theTiO₂ is in place at the surface of a concrete roadway or other concretestructure in close proximity to the roadway, it removes a significantquantity of NOx and VOCs from the environment near their source. If TiO₂is uniformly impregnated into the concrete at depth using a liquidcarrier compound, the pollution-reducing capability of the concrete willautomatically and continuously self-regenerate as the surface layers aresubjected to the normal wear of traffic and other environmental factors.

Traditional methods of NOx reduction (e.g., catalytic converterreduction of motor vehicle emissions) have reached a point ofdiminishing returns in terms of cost effectiveness, resulting in theneed for new and innovative methods of pollutant reduction. A method ofreducing these pollutants may be the use of photocatalytic titaniumdioxide blended into concrete paving mixtures at the time ofconstruction. This method has not seen widespread acceptance orpractical implementation yet for a number of reasons.

One key disadvantage of the method described above is its limitation tousage in freshly placed concrete surfaces, reducing its economicviability for existing roadbeds that are structurally sound, whichcomprise a large percentage of the roadbeds and structures that would bemost subject to violating the forthcoming Environmental ProtectionAgency (EPA) guidelines. The tremendous cost that would be created byreplacing these roadbeds and structures with new concrete would beprohibitive, both in terms of dollar cost and user delays.

The present technology impregnates the concrete with TiO₂ by applyingspecialized proprietary penetrating liquid carriers to the surface of aconcrete structure. These carriers are designed and proven to carrychemicals into concrete. The TiO₂ is blended into the liquid carriers ata proportion that will result in a uniform distribution of TiO₂nanoparticles throughout the upper one-quarter (0.25) inch layer of theconcrete structure, or to other depths according to road or structuredesign requirements. As mentioned above, the combination of liquidcarrier compound and TiO₂ is referred to as a concrete treatmentcompound.

Examples of liquid carrier compounds that may be used for this purposeare Litho1000Ti (for existing, cured concrete) manufactured by PavementTechnology, Inc. and Lithium Cure Ti (for new concrete that is in thecuring process) manufactured by Sinak Corporation.

These carrier compounds have the added benefit of sealing and hardeningthe concrete and filling voids in its structure to increase resistanceto water damage, chloride ion penetration, de-icing salts, andfreeze/thaw damage. In some embodiments, an anatase powder form of TiO₂nanoparticles at a specific concentration is combined with the liquidcarrier that will result in TiO₂ being delivered at the designed rate ofapplication for the impregnated region. To be sure, other penetratingliquid carriers and/or forms of TiO₂, other semiconductors or inorganicpigments that are photocatalytic and alternate concentration levels, canbe employed as deemed suitable.

In some embodiments the concrete treatment compound comprising the TiO₂additive (or other photocatalytic compound) is sprayed or otherwiseapplied to horizontal road surfaces by a sprayer applicator with a spraybar of variable length utilizing industry standard nozzles. Theapplication rate is controlled by a computerized flow manager, whichallows the carrier compound to be precisely applied to the road surface.Once the flow rate computer has been set to the desired applicationrate, the application of the carrier compound is very accurate due tothe computer control of the flow, regardless of travel speed variationsof the sprayer. On vertical surfaces, or other surfaces inaccessible toa sprayer applicator with spray bar, the compound can be applied by handspraying with a wand, or any other suitable means of application thatmaintains the required accuracy.

If conditions in a given application dictate that a horizontal concretesurface requires texturing for safety, adhesion or other reasons,abrasive media application methods will be employed prior to sprayapplication of the liquid carrier compounds. Exemplary methods are theSkidabrader process, conventional shot blasting, diamond grinding, waterblasting, and the like.

In some embodiments, if the concrete surface is damaged or the surfacehas an unacceptable slip coefficient (e.g., a surface texture that islikely to cause an individual to slip and fall on the surface) thesurface to be treated may be textured using the aforementioned abrasiveprocess, or repaired if necessary.

Additionally, the concrete treatment compounds of the present technologycan be applied to a concrete surface without first priming the surface,which is often required for concrete treatment processes such aspainting or sealing.

As mentioned above, the amount concrete treatment compound (e.g.,carrier compound plus photocatalytic material) that is applied to aconcrete surface should be enough to penetrate the concrete down tobetween a depth range of approximately an eighth of an inch toapproximately a half of an inch, inclusive. Further, a concentration ofphotocatalytic material within the liquid carrier compound should besufficient to achieve a desired concentration of the photocatalyticmaterial within the concrete surface. This process of deliveringconcrete treatment compounds is referred to as distributive embedding.

The depth to which the concrete treatment compound should bedistributively embedded may depend upon a variety of factors such as thecomposition and size of the aggregate used to create the concrete or thebinder used to hold the aggregate together. By example, thephotocatalytic material of the concrete treatment compounds may onlyneed to penetrate up to one quarter of an inch for asphalt cement thatincludes an aggregate that is small and tightly packed such that itresists wear off, whereas a cement that is known to wear off quickly mayrequire photocatalytic material to be embedded further into the concreteto account for additional wear. Other factors may include expected oraverage traffic or use patterns that may predict wear off rates, as wellas weather information. Other factors that would be apparent to one ofordinary skill in the art are also likewise contemplated for use.

Thus, in some instances, it is required to calculate an amount ofconcrete treatment compound of the present technology, which will berequired to penetrate the concrete surface down to a sufficient depthrelative to an upper surface of the concrete surface. The examples offactors that affect wear off may be used as a part of this calculation.For example, if it is determined that based upon concrete compositionand traffic pattern that an average wear off of 0.005 inches per year isexpected, and the lifespan of the concrete surface is forty years, theconcrete treatment compound should be applied so as to penetrate to adepth of up to one quarter of an inch, as the expected wear would be 0.2(two tenths) inches over the forty years.

FIG. 1 is a flowchart of an exemplary method of treating concrete toreduce nitrogen oxides (NOx), volatile organic compounds (VOC), andother pollutants.

The method optionally includes preparing 105 the concrete, if necessary,to remove surface contaminants to ensure that the concrete treatmentcompound can adhere to and penetrate the concrete to the depth required.

In some embodiments, the method optionally includes texturing 110 theupper surface of the concrete. Again, this includes, for example, usingan abrasive technique to prepare the surface of the concrete.

The method also comprises mixing 115 at least one solvent compound witha titanium dioxide (TiO₂) photocatalyst. In some instances, the TiO₂photocatalyst is an anatase powder form of TiO₂. The solvent compound ismixed with the anatase TiO₂ so that the TiO₂ is dispersed, allowing theTiO₂ to penetrate the concrete pavement.

The method also comprises applying 120 an amount of concrete treatmentcompound to an upper surface of the concrete. As mentioned above, theconcrete treatment compound comprises a mixture of a liquid carriercompound with the anatase titanium dioxide (TiO₂) photocatalyst. Theliquid carrier compound may include any liquid that can seal and hardenconcrete and fills voids therein to increase resistance of the concreteto water damage, chloride ion penetration, de-icing salts, freeze/thawdamage, and other deleterious effects.

The method includes allowing 125 the treated concrete to dry for aperiod of time.

FIG. 2 is a method for preparing the concrete treatment compound thatincludes calculating 205 an amount of concrete treatment compound thatis necessary to ensure that the concrete is penetrated and embedded withphotocatalytic material to a sufficient depth.

The method also includes selecting 210 a photocatalytic material for theconcrete treatment compound that is capable of reducing an amount ofnitrogen oxides (NOx) and volatile organic compounds (VOC).

The method also includes selecting 215 a carrier liquid for the concretetreatment compound that is capable of penetrating and delivering thephotocatalytic material to a sufficient depth of the concrete. In someembodiments, the method includes mixing 220 the concrete treatmentcompound by combining a liquid carrier compound with an amount of theselected photocatalytic material.

FIG. 3 illustrates an asphalt concrete section 305 that has been treatedwith concrete treatment compound 310. The concrete section 305 is shownas having an upper surface 315. The amount of concrete treatmentcompound 310 has penetrated down from the upper surface 315 to a depthD. This depth D can range anywhere from one sixteenth of an inch, to ahalf of an inch. Other depths may also be utilized and can varyaccording to design requirements and usage.

Other examples of compounds that may be used as carrier liquids includeSurfCrete Ti manufactured by Pavement Technology, Inc., and RELAY Timanufactured by Sinak Corporation. One embodiment of the presenttechnology utilizes an anatase powder form of TiO₂ at concentrations of3% to 5% by weight. The anatase powder form of TiO₂ is mixed with asolvent so that the TiO₂ is dispersed. Other resurfacing compoundsand/or forms of TiO₂, and alternate concentration levels, can beemployed as deemed suitable.

In some embodiments the compound is applied with squeegees to a concretesurface that has previously been roughened with abrasive media, such asthe Skidabrader process, conventional shot blasting, diamond grinding,water blasting, and the like. For thicker applications, the compound isapplied in layers, typically nine (9) mils thick, with each layer beingallowed to dry before the next layer is applied.

While the present technology has been described in connection with aseries of steps, these descriptions are not intended to limit the scopeof the technology to the particular forms set forth herein. It will befurther understood that the methods of the invention are not necessarilylimited to the discrete steps or the order of the steps described. Tothe contrary, the present descriptions are intended to cover suchalternatives, modifications, and equivalents as may be included withinthe spirit and scope of the invention as defined by the appended claimsand otherwise appreciated by one of ordinary skill in the art.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. The descriptions are not intended to limit the scope of thetechnology to the particular forms set forth herein. Thus, the breadthand scope of a preferred embodiment should not be limited by any of theabove-described exemplary embodiments. It should be understood that theabove description is illustrative and not restrictive. The scope of thetechnology should, therefore, be determined not with reference to theabove description, but instead should be determined with reference tothe appended claims along with their full scope of equivalents.

What is claimed is:
 1. A concrete structure, comprising: a concrete bodyhaving an internal structure and a surface; a coating on the surface andextending over the internal structure so as to impregnate the concretebody to a depth greater than ⅛ inch; the coating comprises at least 3%by weight anatase TiO₂ at the depth greater than ⅛ inch; and the anataseTiO₂ is exposed at the surface.
 2. The concrete structure of claim 1,wherein the anatase TiO₂ is co-distributed with a concrete sealer. 3.The concrete structure of claim 1, wherein the anatase TiO₂ exposed atthe surface makes the surface operative to oxidize nitrogen oxides whenthe surface is exposed to sunlight and atmospheric humidity.
 4. Theconcrete structure of claim 1, wherein the coating extending over theinternal structure is uniform through a layer of the concrete body thatis at least ¼ inch thick.
 5. The concrete structure of claim 1, whereinthe concrete structure is functional to photocatalytically reduce anamount of volatile organic compounds around the concrete structure.
 6. Aconcrete structure, comprising: a concrete body having a surface; aphotocatalyst within the concrete body and concentrated near thesurface; wherein the photocatalyst is distributed throughout a layer ofthe concrete body that is at the surface and is more than ⅛ inch thick;and the photocatalyst is exposed at the surface so as to make thesurface active for photocatalytic oxidation of volatile organiccompounds that come in contact with the surface.
 7. The concretestructure of claim 6, wherein the photocatalyst is anatase TiO₂.
 8. Theconcrete structure of claim 6, wherein the surface is a verticalsurface.
 9. The concrete structure of claim 6, wherein the surface is ahorizontal surface.
 10. The concrete structure of claim 6, wherein thephotocatalyst is co-distributed with a concrete sealer.
 11. The concretestructure of claim 6, wherein the photocatalyst is restricted to outerlayers of the concrete body.
 12. The concrete structure of claim 6,wherein any portion of the layer of the concrete body is photocatalyticif exposed by wear.
 13. The concrete structure of claim 6, wherein thelayer is at least ¼ inch thick.
 14. The concrete structure of claim 13,wherein the photocatalyst is uniformly distributed throughout the layer.15. The concrete structure of claim 6, wherein the layer is at least ½inch thick.
 16. The concrete structure of claim 6, wherein thephotocatalyst exposed at the surface makes the surface active forphotocatalytic oxidation of nitrogen oxides that come in contact withthe surface.
 17. A concrete structure, comprising: a photocatalyticallyreactive layer within a concrete body that is otherwisenon-photocatalytically reactive, wherein; the photocatalyticallyreactive layer is at a surface of the concrete body; and thephotocatalytically reactive layer comprises a photocatalyst that isexposed at the surface.
 18. The concrete structure of claim 17, whereinthe photocatalyst impregnates the concrete body co-extensively with aconcrete sealer.
 19. The concrete structure of claim 17, wherein: theconcrete body comprises an aggregate and a binder; and the photocatalystis anatase TiO₂ distributively embedded in the concrete body.
 20. Theconcrete structure of claim 17, wherein the photocatalytically reactivelayer extends at least ¼ inch into the concrete body.